A device of this kind is described, e.g., in U.S. Pat. No. 2,730,770. Here, the device is implemented as a multi-cylinder drafting arrangement for drafting fiber material. The multi-cylinder drafting arrangement comprises three roller pairs that are arranged one behind the other and form a predrafting zone and a main draft zone. In the main draft zone, a bottom apron and a top apron are arranged for guiding the fiber material, wherein the bottom apron and the top apron each revolve around the bottom roller and the top roller, respectively, of the middle roller pair.
For cleaning the surface of the bottom infeed roller and the bottom apron, a clearer roller is arranged in the drafting arrangement between the bottom infeed roller and the bottom roller of the middle roller pair around which the bottom apron revolves. The clearer roller is mounted via two bent spring elements. At the one end, the spring elements are fixedly connected to the frame of the drafting arrangement, and at their other end, they have a U-shaped holder via which the journals of the clearer roller are received. The holders are configured such that the clearer roller journals in the holder can be moved transverse to the clearer roller axis. By means of the spring elements, on the one hand, the clearer roller is brought in contact with the surface of the bottom infeed roller and the bottom apron. On the other hand, the clearer roller is subjected via the spring elements to a pressing force against the surface of the bottom infeed roller, whereby an intensified cleaning efficiency on the surface of the bottom infeed roller is achieved.
In order to ensure a continuously high yarn quality, some of the rollers of the device have to be reground after a certain running time. It is possible here that, depending on the degree of wear, the rollers are reground to a different extent, and as a result, the initial diameter ratio between the rollers changes. In order for the clearer roller to be subjected to a consistent pressing force against the roller surface to be cleaned, the clearer roller thus has to be able to adapt to different diameter ratios of the rollers.
In the device illustrated in U.S. Pat. No. 2,730,770, the bottom infeed roller does not have to be reground due to its metallic surface so that the diameter ratio between the roller does not change during operation. However, the top infeed roller having a rubber coating on its surface has to be reground regularly so as to ensure a continuously high yarn quality. If the clearer roller for cleaning the top infeed roller and the top apron would be arranged between the top infeed roller and the top apron, it therefore would be necessary to adapt the position of the clearer roller to different diameter ratios so as to ensure a consistent cleaning efficiency on the surface of the top infeed roller and the top apron. However, this would not be possible due to the alignment of the spring elements in the drafting arrangement. If the top infeed roller of the drafting arrangement would be reground, the clearer roller would be pressed by the spring elements against the surface of the top infeed roller. Thus, consistent cleaning efficiency of the surface of the top infeed would be ensured. However, due to the diameter reduction of the top infeed roller, the position of the clearer roller would shift towards the top infeed roller. Through this, the distance of the clearer roller from the top apron would increase, which would result in that the cleaning efficiency on the top apron decreases, and a consistent cleaning efficiency of the top apron would no longer be ensured.
Another device of this kind is described in DE 1 833 936 U. Therein, a clearer roller is shown which is provided for cleaning roller surfaces of rollers arranged next to one another at a radial distance. Here, a bent spring element is secured on a top roller support arm of a twin drafting arrangement. The spring element rests against the clearer roller journals of the clearer roller and exerts via that journals a compression force on the clearer roller. The clearer roller therefore is subjected by the spring element to an additional pressing force against the roller surfaces to be cleaned, whereby intensified cleaning efficiency of the clearer roller on the roller surfaces to be cleaned is achieved.
The disadvantage of this embodiment is that by swiveling the top roller support arm upwards, it is not ensured that the clearer roller is lifted off the roller surface to be cleaned since the spring element only loosely rests against the clearer roller journal. This poses the danger that the clearer roller falls out of the device when swiveling the top roller support arm upwards. Thus, prior to swiveling the top roller support arm upwards, the clearer roller has to be removed from the device. In order to nevertheless enable lifting off the clearer roller by means of the top roller support arm, DE 1 833 936 U proposes an embodiment of the spring element in which the clearer roller journals are enclosed by the spring element so that when swiveling the top roller support arm upwards, the clearer roller is swiveled upwards at the same time. However, the solution described in DE 1 833 936 U, which enables lifting off the clearer roller from the roller surfaces to be cleaned, does not contain any indication that in the case of regrinding a roller, the clearer roller is able to adapt to the changed diameter ratios of the rollers so that this device also cannot ensure consistent pressure distribution on the roller surfaces to be cleaned.